Batteries formed having a flat, multicell configuration have been recognized as having a particular utility as a power source for a variety of products. For instance, when efficiently designed and fabricated, the power sources may exhibit a relatively low internal impedance as well as a relatively high current output capacity. These desirable powering characteristics, when coupled with a generally flat geometric configuration, ideally lend such batteries to a use in complement with compact but sophisticated electronically controlled instruments and devices.
As an example of such a union of components, flat primary batteries have been combined with the photographic film packs employed exclusively in a photographic camera sold by Polaroid Corporation of Cambridge, Massachusetts, U.S.A., under the trademark "SX-70". Described, for instance, in U.S. Pat. Nos. 3,705,542; 3,543662; 3,543,663; and 3,595,661, the film packs are formed comprising a disposable cassette structure containing a dark slide for covering an exposure station in a forward wall thereof, a stack of individual self-developing film units positioned behind the dark slide, a spring platen for urging the film units toward the forward wall to position the uppermost one of the film units in the stack at the exposure station and a flat battery positioned opposite to the platen having adjacent terminal surfaces of opposed polarity which are accessible from the rearward wall of the cassette. Thus configured, the film pack is ideally suited as a component within a photographic system incorporating a highly automated camera of complementing compact configuration. Such a camera may include integrated solid state control circuits as detailed in U.S. Pat. No. 3,774,516 which serve a myriad of functions including the control of tractive electro-magnetic drives as described, inter alia, in U.S. Pat. Nos. 3,791,278; 3,750,543; 3,805,204; and 3,820,128. Additionally, the power supply provided the camera permits a utilization of dynamoelectric motor drives and the like as disclosed, for instance, in U.S. Pat. Nos. 3,811,081 and 3,731,608.
For practical utilization, the flat battery structures should be capable of exhibiting efficient performance characteristics without the external application of compressive forces. Alternatives to otherwise necessary compression deriving techniques generally have looked to the incorporation of adhesives, particularly between particulate active electrode materials and current collector surfaces. For instance, in U.S. Pat. No. 3,770,504 particulate electrode material deposited upon a carbon impregnated polymeric current collector surface is adhered thereto utilizing a variety of adhesives. The resultant "patch-type" electrode structures typically are preformed upon the collector surfaces prior to battery manufacture. These assemblies subsequently are combined in combination with gel electrolyte material and the like to form a laminar pile or multicell battery.
A flat battery structure from which enhanced current drain capacities are available is described in copending application of S. A. Buckler, Ser. No. 495,681, filed Aug. 8, 1974, entitled "Flat Battery" and assigned in common herewith. This battery includes both positive and negative active components in an aqueous slurry form as particulate dispersions with electrolyte and a hydrophilic polymeric binder or dispersant. The electrode particles within the slurry are present in a concentration per unit area which is effective to provide an electrically conductive dispersion and, in consequence of the higher surface availability of electrode materials within the electrochemical system, batteries of a desirably broad range of current capacities are readily designed and manufactured. For instance, one such manufacturing technique, described in copending U.S. application for U.S. Pat. No. by O. E. Wolff, Ser. No. 514,458, filed Oct. 15, 1974 and entitled "Method for Forming A Slurry Battery Cell", also assigned in common herewith, describes that the slurry battery structures may be formed in situ as a step in fabrication of a laminar pile assembly.
In a copending application for U.S. Pat. application Ser. No. 495,628, filed Aug. 8, 1974, by E. H. Land, and now abandoned entitled "Flat Battery", assigned in common herewith, another flat battery structure of enhanced output capacity is described as incorporating a laminar cell structure having a planar cathode assembly including a current collector carrying on one surface, in order, a first cathode mix comprising a particulate dispersion of cathode mix particles in a binder matrix and a second cathode mix comprising a particulate dispersion of cathode mix particles with hydrophilic binder disposed within aqueous electrolyte, i.e., in slurry form. In this hybrid form of slurry electrode structure, a highly desired improved shelf-life characteristic is evidenced in combination with advantageously higher output capacity.
Practical introduction of such batteries as are above described to the marketplace requires that they be manufacturable utilizing relatively high volume techniques. Additionally, because of such intended uses as a component of a film cassette assemblage or the like, a relatively high degree of reliability is required for all batteries produced. One successful manufacturing technique, as is described in a copending application for U.S. Pat. application by L. O. Bruneau, Ser. No. 478,106, filed June 10, 1974, entitled "Flat Battery and Manufacture Thereof", and assigned in common herewith, describes the provision of an electrically insulative continuous carrier upon which pile buildup is carried out utilizing discrete cell components, i.e. polymeric electrically conductive intercell connectors, separators and externally disposed metal-conductive polymeric material current collector assemblies, portions of the metal surfaces of which may serve as terminals for the resultant batteries.
A wide, continuous web approach to multicell battery assembly is described, for instance, in U.S. Pat. No. 3,708,349. As set forth therein, the wide carrier web utilized is a conductive polymeric material, i.e. a carbon impregnated vinyl or the like, having various designated zones, some of which are laminated with a continuous sheet metal strip to form collector assemblies as described, for instance, U.S. Pat. No. 3,741,814. Utilization of duplex electrodes in combination with the noted patch-type active material depositions is described, for instance, in U.S. Pat. Nos. 3,694,266 and 3,770,505, while the noted metal-electrically conductive polymeric externally disposed current collector assemblies are described, for instance, in the noted U.S. Pat. No. 3,741,814. The separator arrangement for providing pile buildup in the method described in the noted U.S. Pat. No. 3,708,349 also is of wide web variety utilizing a preimpregnation of border sealant as described in U.S. Pat. No. 3,784,414.
While the utilization of a continuous wide web of electrically conductive polymeric material as the carrier for a battery manufacturing process would appear to lend itself to advantages in achieving high volume manufacturing rates, yields of reliable batteries in sufficient quantity may be difficult to realize. For instance, the continuous metal-electrically conductive polymer laminate zones of the carrier web necessarily provide for an electrical interconnection of all electrochemically active pile components developed in the course of manufacture. In consequence, voltage buildup phenomena and the like may be witnessed along the assembly line which may derogate from battery performance and, consequently, production system reliability. Additionally, difficulties may be encountered in severing the finally produced discrete batteries from the continuous production line by the development of intercell shorting effects and the like. Further, the polymeric material utilized as the carrier web necessarily is somewhat pliable and difficult to transversely and laterally control so as to achieve necessary registration during assembly of the components of the multicell batteries.